Embodiments of the present technique relate generally to physiological monitoring, and more particularly to system and methods for improving physiological parameter estimation using a multi-wavelength optical transducer array.
Continual monitoring of a patient's physiological parameters such as vital signs and/or overall health allows for accurate diagnoses and immediate alerts for life saving interventions. Particularly, routine use of multi-parameter monitors in trauma, surgery, and intensive-care unit (ICU) settings has greatly improved medical outcomes in recent times. Pulse oximeters, for example, may be used to monitor oxygen saturation (SpO2) in arterial blood. Particularly, pulse oximeters may be used to provide instantaneous measurements of arterial oxygenation to allow early detection of medical conditions such as arterial hypoxemia.
Generally, the SpO2 measurements may accurately represent the arterial oxygen saturation, even while the oxygen carrying capacity of the blood is reduced due to low overall hemoglobin concentration. However, in certain scenarios, use of only the SpO2 reading can be misleading and the oxygen supply to tissues may still be inadequate regardless of the high SpO2 value. Conventional pulse oximeters, for example, may report erroneous SpO2 measurements due to similarities in the absorption spectra of the oxygen carrying hemoglobin and dysfunctional hemoglobin (dyshemoglobin) such as Carboxyhemoglobin (HbCO) and Methemoglobin (HbMet), which are incapable of binding oxygen.
Accordingly, certain pulse oximeters have been customized to generate multiple wavelength photoplethysmographic (PPG) pulse waveforms, which may be related to tissue blood volume and blood flow at a measurement site. The customized pulse oximeters use emitters sensitive to different wavelengths for determining physiological parameters that provide useful clinical information. However, such custom devices often are suited only for a specific application, have poor adaptability to different device configurations, and/or are prohibitively expensive for routine use.
Furthermore, typical PPG-based systems are relatively large devices including a sensor attachable to the patient and the PPG device through one or more cables. Conventional PPG devices measure physiological parameters such as different hemoglobin fractions by disposing the sensor on an anatomical extremity, such as the patient's fingertip or ear. To that end, the sensor may generally comprise two or more emitter elements, each emitting radiation at a specific wavelength, connecting cables and a broad spectral band photodetector common to all emitter elements for multi-analyte measurements.
Specifically, a multiple wavelength PPG device requires measurements at a plurality of combinations of wavelengths and different emitter and detector placements to measure different substances in blood without the disruptive effects of tissue motion. A large variety of sensor types sensitive to different wavelengths, thus, may be needed to suit different subjects and different measurement sites. Accordingly, the choice of sensors and corresponding interface cables that may be used in connection with one pulse oximeter device may be rather extensive, thus impeding the portability and cost-effectiveness of the device. Additionally, the complicated reconfiguration of the pulse oximeter device for appropriately selecting and positioning the sensors and cables at the patient extremity for making a plurality of measurements may significantly add to patient discomfort.
Due to cost and complicated configuration concerns, conventional pulse oximeters are typically known to be used only in hospital environments by experienced medical professionals. Use of the pulse oximeters outside of high acuity hospital wards, however, has been limited owing to unsuitable power consumption, cost, form factor, and performance of the devices. In particular, power and performance of such physiological monitors may be limited by conventional device configurations, while corresponding measurements may often be distorted by tissue motion artifacts.
Accordingly, low-power physiological monitors conducive to portable applications and capable of mitigating motion-induced artifacts and noise for allowing accurate multi-analyte detection and monitoring are desirable.